Coupling nut



FIG. 1 is a top plan view of a coupling nut in accordance with my design;

FIG. 2 is a top, front, left perspective view thereof;

FIG. 3 is a bottom view thereof;

FIG. 4 is a bottom, right, rear perspective view thereof;

FIG. 5 is a front elevational view thereof, with the rear elevational view being identical thereto; and,

FIG. 6 is a right side elevational view thereof, with the left side elevational view being identical thereto.

The broken lines represent portions of the structure that form no part of the claimed design. 

CLAIM The ornamental design for a coupling nut, as shown and described. 